1. Field of the Invention
The present invention relates to an ultrasonic motor.
2. Description of the Related Art
There have been proposed ultrasonic motors that generate an elliptical vibration by combining a longitudinal vibration and a torsional vibration, and rotate a rotor.
For example, in an ultrasonic vibrator disclosed in Patent Application Laid-open No. H9-85172, a pair or a plurality of pairs of multilayered piezoelectric elements is held between holding elastic bodies that are provided integrally with a basal elastic body, and that have a recessed portion in which the multilayered piezoelectric element can be inserted. Furthermore, the multilayered piezoelectric elements are fixed to the basal elastic body with screws in a state in which a compressive stress is applied with the holding elastic bodies abut on piezoelectric elements.
However, the ultrasonic vibrator disclosed in Japanese Patent Application Laid-open No. H9-85172 has various drawbacks. For example, the holding elastic bodies are required for fixing the piezoelectric elements and an oblique recessed portion must be formed in the elastic bodies for arranging the holding elastic bodies and the piezoelectric elements. Thus, the overall structure of the conventional vibrator is very complicated.
Furthermore, a plurality of the piezoelectric elements for detecting vibrations is arranged between a plurality of the pairs of the multilayered piezoelectric elements and the holding elastic bodies, and when driving such a vibrator, two wirings are required for driving a piezoelectric element for driving and two wirings are required for detecting the vibrations of the piezoelectric element for detecting vibrations, thus requiring at least eight wirings. Because of the many wirings required for driving the vibrator, downsizing the ultrasonic vibrator cannot be achieved.